5-羟色氨酸(英语：5-Hydroxytryptophan，5-HTP)，(INN商品名：oxitriptan )是一种天然的氨基酸代谢中间产物，同时也是神经递质5-羟色胺与褪黑素的生物合成前体。

5-羟色氨酸在美英以及加拿大以非处方药方式出售，作为帮助抑郁症、厌食症及失眠患者的膳食补充剂，同时也作为治疗重性抑郁障碍的药物在欧洲许多国家销售。几个安慰剂双盲临床试验已证明5-HTP有治疗抑郁症的效果，但缺乏极显着性，需要更进一步的大量临床对照研究。

5-Hydroxytryptophan (5-HTP), also known as oxitriptan (INN), is a naturally occurring amino acid and chemical precursor as well as a metabolic intermediate in the biosynthesis of the neurotransmitters serotonin and melatonin from tryptophan.